1. Field of the Invention
The present invention concerns an improved variometer, of a type similar to the one shown in U.S. Ser. No. 113,829 the disclosure of which is incorporated by reference herein.
2. Discussion of the Prior Art
One recalls that the variometer according to the abovementioned application or principal patent comprises essentially a dial including in a standard way a scale representative of a vertical speed, a needle indicating on the said scale the instantaneous vertical speed of the aircraft, an indicator representative of the potential vertical speed, which is moveable around the dial and whose position in relation to the needle indicates instantaneously the acceleration on the trajectory of the aircraft, and can also include an indication by a digital display of the gradient of the airplane.
In such a variometer, the signal representative of the instantaneous vertical speed is obtained by means of a calculation member producing the equation ##EQU2## equation in which hx.degree. is the signal of the instantaneous vertical speed of the aircraft;
h.degree.A is a signal of the vertical speed coming from a central anemometric unit; PA1 .tau..sub.1 is a time constant; PA1 .tau..sub.2 is a time constant; PA1 s is the Laplace operator; PA1 J.sub.z is the component of acceleration on the vertical axis which can be provided by an inertial guidance unit. PA1 g is the acceleration of gravity; PA1 V.sub.x is the ground speed supplied by a central inertial unit. PA1 g is the acceleration of gravity; PA1 .phi. is the angle of roll of the airplane. PA1 II: V.sub.H is a composite speed which has for its expression: ##EQU6## the expression TAS designating the True Air Speed of the aircraft; .tau.'.sub.1 and .tau.'.sub.2 being constants of time; PA1 .theta. being the longitudinal position of the aircraft; PA1 j.sub.x.sbsb.1 being the component of the acceleration on the longitudinal axis of the aircraft; PA1 s being the Laplace operator; PA1 III: dVx/dt consists of a mixture of the derivative of the true speed of the aircraft and of the longitudinal accelerartion compensated for gravity, the expression dVx/dt being of the form: ##EQU7## in which .tau..sub.3 is a time constant.
Moreover, the signal representative of the potential vertical speed h.degree..sub.T of the aircraft is obtained in carrying out by means of a calculation member of an equation in the form: ##EQU3## formula in which hx.degree. is the instantaneous vertical speed of the aircraft;
By reason of the nature of the parameters which it utilizes, and in particular of the ground speed V.sub.x and of the component J.sub.z of the acceleration, the variometer according to the principal patent applies esentially to aircraft equipped with an inertial guidance unit.